# what happens when a router receives a packet with a ttl of 0?

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At what layer of the OSI model would a TCP or UDP header be added to a payload?Layer 4
A globally unique number that identifies an autonomous system. ASNs work similarly to IP addresses that identify individual nodes on a network. Each ASN now consists of 32 bits instead of 16 bits, and they are assigned by IANA.autonomous system number
The largest IP packet size in bytes allowable by routers in a path without fragmentation and excluding the frame size.MTU (maximum transmission unit)
A repeated trial message transmitted by the tracert and traceroute utilities to trigger routers along a route to return specific information about the route.probe
A router that connects an autonomous system with an outside networkfor example, the router that connects a business to its ISP.interior router
Properties of a route used by routing protocols to determine the best path to a destination when various paths are available. Routing metrics may be calculated using any of several variables, including hop count, bandwidth, delay, MTU, cost, and reliability.routing metric
The router on a network that accepts all unroutable messages from other routers.gateway of last resort
The delay between the transmission of a signal and its receipt.latency
A process whereby routers learn about all of the devices on their networks. On IPv4 networks, this process is managed by ARP with help from ICMP. On IPv6 networks, NDP (Neighbor Discovery Protocol) automatically detects neighboring devices and automatically adjusts when nodes fail or are removed from the network.neighbor discovery
A router that directs data between networks within the same autonomous system.gateway router
A number indicating a protocol's reliability, with lower values being given higher priority. This assignment can be changed by a network administrator when one protocol should take precedence over a previously higher-rated protocol on a network.administrative distance
The IP connectionless protocol relies on what other protocol to guarantee delivery of data?TCP
What address does ARP work in conjunction with IPv4 to discover?Physical and MAC
What command can be used on a Cisco router to view the routing table?show ip route
What field in an IPv4 packet informs routers the level of precedence they should apply when processing an incoming packet?Differentiated Services (DiffServ)
What netstat command option lists only current connections, including IP addresses and port numbers?-n
What two fields below are used by IPv4 and IPv6 respectively to limit the number of times that a packet can be forwarded on a network?TTL and Hop limit
What versions of the IP protocol are used on networks today?IPv6 and IPv4
Which layers of the OSI model are all routers able to interpret?Layer 3 and 4
Which network routing protocol is a path vector protocol that sends updates between routers using TCP?BGP
___'s lack of sophistication makes it more efficient than TCP.UDP
A _______ joins two or more networks and passes packets from one network to another.Router
A modern ASN consists of how many bits?32
As a network support technician, you only need to know how to support IPv6.False
By default, the pathping command sends how many pings per hop?100
Interior RoutersDirect data between networks within the same autonomous system.
Border RoutersConnect an autonomous system with an outside network
Exterior routersDirect data between autonomous systems
Describe the OSPF routing protocol.OSPF (Open Shortest Path First) is an IGP and a link-state routing protocol used on interior or border routers. It was introduced as an improvement to RIP and can coexist with RIP (or RIPv2) on a network. Unlike RIP, OSPF imposes no hop limits on a transmission path. Also, OSPF uses a more complex algorithm for determining best paths than what RIP uses. Under optimal network conditions, the best path is the most direct path between two points. If excessive traffic levels or an outage preclude data from following the most direct path, a router may determine that the most efficient path actually goes through additional routers. Each router running OSPF maintains a database of the other routers' links. If OSPF learns of the failure of a given link, the router can rapidly compute an alternate path. This calculation demands more memory and CPU power than RIP would, but it keeps network bandwidth to a minimum and provides a very fast convergence time, often invisible to users. The algorithms used by link-state protocols and their faster convergence time also prevent routing loops. OSPF is supported by all modern routers. Therefore, it is commonly used on autonomous systems that rely on a mix of routers from different manufacturers.
Describe the difference between dynamic ARP table entries and static ARP table entries.An ARP table can contain two types of entries: dynamic and static. Dynamic ARP table entries are created when a client makes an ARP request that could not be satisfied by data already in the ARP table. Static ARP table entries are those that someone has entered manually using the ARP utility.
ICMP (Internet Control Message Protocol) is a _______ layer core protocol that reports on the success or failure of data delivery.Network Layer
IP is an unreliable, connectionless protocol.True
IPv4 and IPv6 use the same packet format.False
In IPv6, what field is used to indicate what sequence of packets from one source to one or multiple destinations a packet belongs to?Flow Label
In a TCP segment, what field indicates how many bytes the sender can issue to a receiver while acknowledgement for the segment is outstanding?Sliding window
List some examples of routing metrics that might be used to determine the best path for data.Routing metrics-Hop count, throrectical bandwidtth and actual throughpout on a potential path, Delay, or latency, on a potential path, which results in slower performance, load or the traffic or processing burden sustained by a router in the path.
On IPv4 networks, IGMP operates at the Network layer of the OSI model to manage multicasting.True
The TCP ___________________ is performed before TCP transmits the actual data.Three-way handshake
The receiving host de-encapsulates the message at each layer in _______ order and then presents the payload to the receiving application.Reverse
UDP provides error checking, but not sequencing.False
What IPv4 protocol handles multicasting for tasks such as videoconferencing or teleconferencing?IGMP
What TCP field below allows the receiving node to determine whether a TCP segment is corrupted during transmission?Checksum
What happens when a router receives a packet with a TTL of 0?The router drops the packet and sends an ICMP TTL expired message back to the host.
What is NOT one of the three characteristics of TCP in its role as a reliable delivery protocol?Framing
What is the difference between static and dynamic routing?Dynamic Routing- Automatically calculates the best patch between two networks and accumulates this information in the routing table Static Routing- Is a technique in which a network admin configues a routing table to direct messages along specific paths between networks.
What parameter can be combined with the traceroute command to instruct it to use ICMP echo requests instead of UDP datagrams?-I
What protocol replaces ARP, IGMP, and ICMPv4 on IPv6 based networks?ICMPv6
What routing protocol criteria is defined as the time it takes to recognize a best path change in the event of a network outage?convergence time
What type of routing protocol enables routers to communicate beyond neighboring routers, allowing each router to create a map of an entire network?link state
When viewing the routing table on a UNIX system, what flag indicates if a route is a usable route?U
Which of the following are types of entries an ARP table contains?Static and Dynamic
Which of the following is not a task handled by a router?A router forwards broadcasts over the network.
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